Mott physics and first-order transition between two metals in the normal state phase diagram of the two-dimensional Hubbard model

TL;DR

This paper uncovers a first-order transition between two metallic phases in the doped two-dimensional Hubbard model, revealing a complex normal-state phase diagram with implications for high-temperature superconductors.

Contribution

It demonstrates the existence of a finite-temperature first-order transition surface between two metals in the doped 2D Hubbard model using cellular dynamical mean-field theory.

Findings

Identification of a first-order transition surface between two metals

Presence of a finite-temperature critical line ending at the Mott point

Thermodynamic and scattering signatures associated with the transition

Abstract

For doped two-dimensional Mott insulators in their normal state, the challenge is to understand the evolution from a conventional metal at high doping to a strongly correlated metal near the Mott insulator at zero doping. To this end, we solve the cellular dynamical mean-field equations for the two-dimensional Hubbard model using a plaquette as the reference quantum impurity model and continuous-time quantum Monte Carlo method as impurity solver. The normal-state phase diagram as a function of interaction strength $U$, temperature $T$, and filling $n$ shows that, upon increasing $n$ towards the Mott insulator, there is a surface of first-order transition between two metals at nonzero doping. That surface ends at a finite temperature critical line originating at the half-filled Mott critical point. Associated with this transition, there is a maximum in scattering rate as well as thermodynamic signatures. These findings suggest a new scenario for the normal-state phase diagram of the high temperature superconductors. The criticality surmised in these systems can originate not from a T=0 quantum critical point, nor from the proximity of a long-range ordered phase, but from a low temperature transition between two types of metals at finite doping. The influence of Mott physics therefore extends well beyond half-filling.